What is the purpose of 'Mushrooms'?

I know that mushrooms are ‘fruiting bodies’ of fungi, but I recently I began to think about what they actually do. I do know (or assume) that they spread spores, but why? Are the spores dispersed by wind, insects, or do they just drop at the bottom of the mushroom (many of which do not seem to last long: < 1 day). If so, what is the point of that if there is already an intact sub-surface ‘colony’?
I know very little about fungi, and some do not seem to have a ‘mushroom’ stage. Could someone explain their function (in terms of life cycle) to me? Inquiring minds and all that. I find them kind of fascinating.

13 Likes

They can also be dispersed by water and other animals besides insects

3 Likes

But how far would they be dispersed by water?

Feed this pretty boy, its beetle kin and many other fungi related organisms (springtails, etc)

6 Likes

Spores made in a mushroom are the product of sexual reproduction, so they are genetically different than the parent fungus. Thus, like the seeds made by a flowering plant, they provide genetically diverse offspring so that if the environment changes, hopefully some of the offspring will have a good combination of alleles and will ensure that the genes of the parent continue to get passed on.
A mushroom is also used for spore dispersal, kind of like a fruit with seeds. I’m not sure exactly how it works, but the cells that hold the spores have a trigger-like mechanism that they use to shoot the spores off, and then the spores are caught in air currents and drift away, thus spreading the genes of the parent fungus far and wide. Natural selection favors those who reproduce the most.

11 Likes

So, how does a sub-surface fungus reproduce sexually? How does the other genetic material get to the fungal cells?
I’m not contradicting you - I just don’t understand how it all works!

1 Like

As it’s a part of mycology course, you can find many graphics with what you ask about.

2 Likes

I think the “why” is probably heavily debated enough that it’s not settled. I know the mushroom colour debate is far from settled. Probably no one size fits all answer that applies to all mushrooms, but my short answer is to get spores as far away as possible.

Setting a little parameter here, for the sake of this post i’m defining mushroom as a cap and stem fungus that grows from the ground.

There’s a bunch of various different fungal reproductive strategies that have independently evolved, and the more (not necessarily most) effective structures get passed on most.
I believe the mushroom shape is so common is because it’s easier for animals to see and eat than say, a more resupinate fungi, so is less dependent on the wind to disperse the spores.
This may be why I see less variety in hard, woody polypores, which would be much harder to eat and spread via feces (in as high volumes) compared to say, a Russula which anything from slugs to mice to deer can eat, so can fit into more trophic effects.

Many fungi are clearly set up to take advantage of wind though. Here we can see a cup fungus that’s got mechanical mechanisms to react to wind, so that it doesn’t waste energy on spores that won’t blow far away.

The ones that have very short lifespans are doing something similar to the cup fungi where they’re conserving resources until the right conditions for reproduction occurs, and wanting to take advantage of it only at exactly the right time. A slower growing mushroom like a red belted polypore which takes years to grow would not have this strategy.
That said, I’m less sure of the advantages for perennial growth. I’d assume that its spores are just less picky about heat/moisture conditions, so putting out spores all the time might be better than picking a time, and help them outcompete more sensitive reproducers.

Sorry I didn’t firmly answer anything, but there’s probably no firm one size fits all answer anyway ;)

but ask this question 10 times and places and you’ll get like 6 answers

6 Likes

My understanding is that in at least some commercially cultivated species, the mycelium doesn’t produce mushrooms until food supplies begin running low, and in other species subsequent flushes are triggered when they’re soaked in water. The mycelium may only fruit because it’s out of resources.

Spore dispersal reminds me a bit of island biogeography. It’s a search for more patches of food/better conditions.

4 Likes

In some cases they fruit due to physical shock, such as with Shiitake mushrooms. Their mycelium can detect their host tree crashing to the ground, and decide to fruit then.

4 Likes

I’ve recently read a bit about fungal spore liberation and everything I’ve seen suggested that the “toadstool” shape has two primary functions: protecting the hymenium from rain (as unlike in ascomycetes, most basidiomycete hymenia don’t work very well when wetted) and to enable the spores to drop into an airmass with turbulent flow rather than the laminar flow of the thin layer of air right above the ground (which ascomycete cup fungi with their much more powerful spore release mechanism can punch through) - in other words a specialisation for wind dispersal in places where the wind is hard to get to rather than away from it.

That consumption by animals should be a main driver also doesn’t seem to make much sense to me when you consider that most toadstools drop their spores actively and continually rather than build up a spore mass like e.g. truffles (with the result that a rather small proportion of the total potential production would be eaten regardless of the moment of consumption).

6 Likes

The pretty boy is now full and ready to fly to another place

It got covered by some spores in the process and will make the fungus appear somewhere else.

Springtails also take a ride on them and other kind of beetles/insects, and end up spreading the fungus to places the wind can’t go.

So yeah it is not just by eating, but the appetizing bits of the fungus probably evolved to lure these guys here so that they get a shower of spores on them. Pretty much like those “seemingly-carnivorous” plants trap the insects in some bag where they get loaded with pollen.

4 Likes

Based on what I know about ascomycetes (cup fungi) and basidiomycetes (mushrooms), when a spore lands in a good spot, it germinates and forms haploid mycelium that grows and digests its way through the substrate until it encounters another, genetically compatible, haploid mycelium. They fuse together and swap copies of their nuclei, so that you end up with one big fungus that has two nuclei in each cell. Now, whenever conditions are right, it can build a mushroom, and in that structure, the paired nuclei fuse to make diploid nuclei. Those nuclei undergo meiosis, and the result is haploid spores that now have a mix of genetic material from both original haploid mycelia.

5 Likes

Function: decomposition in good part, the great recyclers. Without fungi the organic debris in the forests and elsewhere would pile up and take much longer to break down into usable nutrients. Some fungi consume the lignin in logs, others cellulose. There are numerous that live on the duff where ones ecosystem is a Douglas-fir needle or oak leaf.
The fruit bodies feed not only insects but slugs and snails, rodents and other mammals.
Hypogeous fungi tend to be odoriferous when mature so small rodents will find and eat them thus dispersing spores with a nice nutrient packet.

1 Like

So some of the spores are spread by animal faeces?

So the genetic swapping occurs with the mycelium? Is it then that the mushrooms emerge?

It’s a bit different between ascomycetes and basidiomycetes. The “one big fungus with 2 sets of nuclei per cell” only happens in basidiomycetes, not ascomycetes. I.e. only basidiomycetes can be dikaryotic. In ascomycetes the mycelium remains monokaryotic until fusion occurs within the developing ascus.

The formation of fruitbodies is triggered by many factors.

3 Likes

I don’t think fungi are so fond of anything eating them, they release spores on wind and don’t get any clear advantage from being eaten, Russula will be eaten in a day by a slug and will just loose potential to spread spores, polypores also won’t get anything from tenebrionids eating their insides, animals also can’t spread spores as effectively and far as wind.

1 Like

We are eating road kill?
On second thoughts, we are eating the rising phoenix.

2 Likes

I’ve read something about a study in Patagonia that showed that birds were discovered to be a much more major disperser of mushroom spoor than expected.

Also, while technically not a mushroom, truffles achieve high dispersion radii through flying squirrels who seem to be excellent at memorizing the locations and development stages of these culinary treasures.

3 Likes